Planting date and cultivar selection to manage southern blight in potatoes in the mid-Atlantic United States

Authors: GARCIA-GONZALEZ, JOSE - Virginia Tech; Mehl, Hillary; LANGSTON, D - Virginia Tech; RIDEOUT, STEVE - Virginia Tech

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2022
Publication Date: 8/22/2022
Citation: Garcia-Gonzalez, J., Mehl, H.L., Langston, D.B., Rideout, S.L. 2022. Planting date and cultivar selection to manage southern blight in potatoes in the mid-Atlantic United States. Crop Protection. 162. Article 106077. https://doi.org/10.1016/j.cropro.2022.106077.
DOI: https://doi.org/10.1016/j.cropro.2022.106077

Interpretive Summary: Incidence of the soilborne disease southern blight is increasing across the US mid-Atlantic region and threatening potato production sustainability. Management relying on fungicides and fumigants has been inconsistent and uneconomical, and no cultivars are known to be resistant to southern blight. To identify disease management alternatives, this research evaluated the effects of planting date and cultivar selection on potato losses due to southern blight. Delaying planting until mid-April to May resulted in greater disease incidence and reduced tuber yield and quality. Humid and warm weather conditions associated with later planting dates led to greater disease development and likely hindered potato tuber development. Though no cultivar was completely resistant to southern blight infection, chipping cultivars tended to be more resistant than fresh market cultivars. This study demonstrated that the practice of planting less susceptible cultivars prior to the first week of April is an effective and economical approach to minimize potato losses to southern blight in the mid-Atlantic US.

Technical Abstract: Incidence of southern blight caused by Sclerotium rolfsii Sacc. in potato (Solanum tuberosum L.) has increased across the mid-Atlantic region. To date, no potato cultivar is resistant to southern blight, and effective management with fumigants and fungicides has been inconsistent and uneconomical. This study evaluated impacts of four planting dates, ten commercial cultivars, and integrated effects of planting date and cultivar on southern blight incidence, yield, and tuber quality. Disease incidence varied by year, with fewer occurrences in 2019 (25%) than in 2018 (79%) or 2017 (64%), likely due to dry and warm weather. Despite the planting date by cultivar interaction, later plantings had greater disease incidence (85–94%) and lower tuber yield (1.8–9.4 Mg ha-1) and quality (47–78% marketable tubers) than earlier plantings. Planting date effects were likely driven by humid, warm weather later in the season that was conducive to disease and detrimental to crop development. Though cultivar responses varied across planting date-years, ‘Accumulator’ had the lowest disease incidences (36%) and greatest tuber yield (20.2 Mg ha-1) among tested cultivars. Conversely, ‘Adirondack Blue’ and ‘Dark Red Norland’ had the overall greatest incidence of S. rolfsii (33–100%) while ‘Yukon Gold’ had the lowest yield (0.3–24.1 Mg ha-1). Potato chipping cultivars tended to be less impacted by S. rolfsii than fresh market cultivars; however, additional studies are needed to elucidate potential mechanisms of disease resistance. This study indicates early planting dates and cultivar selection are an effective management approach to reduce S. rolfsii incidence on potato and maximize tuber yield.